1. Field of the Disclosure
This disclosed device and method relates generally to a transfer station used in continuous web electrostatographic or xerographic printing systems.
2. Description of Related Art
The use of BTR (Biased Transfer Roll) foam rollers, disposed in contact with a portion of a photoreceptor, as well as transfer blades and dicorotrons, are often used in the prior art to pull an image from a PR belt or drum to paper. In continuous paper web feeding, however, a difficulty in printing onto a continuous web substrate is the fact that belt type photoreceptors typically have a belt seam. To avoid the seam on the belt, in the prior art, It has been necessary stop the web movement, reverse the web direction, and then reverse direction again to maintain synchronization of the PR belt and continuous web, as the seam passes through the transfer station. This movement of the large mass of the paper roll is a complex process that inhibits speed of operation of the printing system and poses unnecessary risk of web malfunctions.
It is known, as disclosed in U.S. Pat. No. 5,970,304, buffers and dancer rolls are known for the buffering of web speed variations and also the separation of the web from the nip to adjust the relationship of the photoreceptor belt and web for facilitating the transfer of images from the belt to the web. Also, current designs generally require the continuous web to separate, stop, back up, and reverse again and remerge with the PR belt in order to skip the seam on the
Thus, in accordance to the present disclosure, a system is provided that avoids any stopping or reversing of the web direction in a continuous feed printer, instead maintaining more consistent process speed. The only requirement is a moderate slowing and speeding up of the web, in order to cycle through the PR belt seam. This is done by forming an adjustable loop in the continuous web and then immediately flattening the loop after passage of the seam through the transfer zone. The transfer zone includes two transfer BTR rolls with selective transfer operations. Two vacuum assist rolls control the formation and size of the web loop. These advantages allow a relatively simple operation to cycle through the PR belt seam.